v3.26.1
Document and Entity Information - shares
 6 Months Ended
Jun. 30, 2026
Aug. 19, 2026
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2026  
Document Transition Report false  
Entity Registrant Name Avalanche Treasury Corporation  
Entity Incorporation, State or Country Code DE  
Entity File Number 001-43345  
Entity Tax Identification Number 39-4863126  
Entity Address, Address Line One 11 W. 42nd Street 2nd Floor  
Entity Address, City or Town New York  
Entity Address State Or Province NY  
Entity Address, Postal Zip Code 10036  
City Area Code 332  
Local Phone Number 240-1155  
Title of 12(b) Security Class A common stock, par value $0.01 per share  
Trading Symbol AVAT  
Security Exchange Name NASDAQ  
Entity Current Reporting Status No  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Central Index Key 0002092446  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Class A common stock    
Entity Common Stock, Shares Outstanding   37,914,805
Class B common stock    
Entity Common Stock, Shares Outstanding   5,805,639